function creaXMLHttpReqObj(){
	if(window.XMLHttpRequest){
		xmlHttpObj=new XMLHttpRequest();
	}else{
		try{
			xmlHttpObj = new ActiveXObject("Microsoft.XMLHTTP");
		}catch(e){
			xmlHttpObj = new ActiveXObject("Msxml2.XMLHTTP");
		}
	}
	return xmlHttpObj;
}

/* Valores comunes para ReadyState del objeto XMLHttpRequest */
var READYSTATE_UNINITIALIZED = 0;
var READYSTATE_LOADING = 1;
var READYSTATE_LOADED = 2;
var READYSTATE_INTERACTIVE = 3;
var READYSTATE_COMPLETE = 4;

var HTTPSTATUS_OK = 200;


// variable XMLHttpRequest global
var xmlHttpObj = creaXMLHttpReqObj();